Having a rifle that chambers the same ammo as the one used in your sidearm is very practical...

It may be convenient for reloaders or stock piles and may of been practical 150 years ago in the boonies but practical is a stretch. You can only handle one gun at a time, doesn't make a spits worth of difference if any other gun you have fires the same cartridge. When is it even possible to be in a situation where that commonality would be an asset? Not in the field, not at home, not in the car, not at work...........

Not to say that handgun/carbine combo's aren't cool. I love em. But practical went out the window with long term wilderness survival.